This invention relates to an improved plug container for well cementing operations.
Prior to the cementing of casing in an oil or gas well, in most instances, continuity of the circulation of fluids in the well bore around the outside of the casing from the interior thereof is desired as a precautionary measure to help in preventing the casing from sticking. Rather than opening the top of the casing to insert cementing plugs therein prior to the cementing operation, a plug container in which the cementing plugs are initially contained is installed on the top of the casing having flow lines and cementing lines connected thereto.
A typical prior art plug container is shown in Halliburton Sales and Service Catalog Number 39, page 3138. The prior art plug container shown on page 3138 is designed for continuous operation in casing cementing operations. The bottom cementing plug is inserted through the plug container into the casing before the mixing of cement starts. The top cementing plug is inserted or loaded into the plug container, resting on the releasing pin contained therein, at the same time as the insertion of the bottom cementing plug. The top cementing plug is released to follow the cement down the casing, by turning the releasing handle connected to the releasing pin. A lever type indicator installed in the plug container shows the passage of the top cementing plug as it leaves the plug container and enters the casing.
The design of this prior art plug container permits the use of multiple plug containers in series, the top thread of one mating with the bottom thread of the other, after the removal of the lower nipple from the upper plug container. In this manner, a double plug container is created having continuous operating capabilities. Utilizing a double plug container, the bottom cementing plug is released ahead of the cement while the top cementing plug is released behind the cement.
Typically, this prior art plug container is constructed from a casting having the fluid inlet ports to the plug container being located approximately perpendicular to the bore through the plug container through which the cementing plugs pass. While this prior art plug container is simple to construct, obtaining crack-free castings to manufacture the plug container can be a problem. Also, since the fluid inlets to the plug container enter approximately perpendicular to the bore of the plug container, in some instances, the cementing plug may never be pumped down the casing after being released by the releasing pin because the cementing plug may float in the plug container on the cement being pumped therethrough without being carried downwardly therewith.
Another typical prior art plug container is constructed as a weldment having the fluid inlet ports to the plug container being located approximately perpendicular to the bore through the plug container through which the cementing plugs pass. Since this plug container is simple to construct and is fabricated as a weldment, it is not subject to cracks during casting operations. However, since the fluid inlets to the plug container enter approximately perpendicular to the bore of the plug container, in some instances, the cementing plug may never be pumped down the casing after being released by the releasing pin because the cementing plug may float in the plug container on the cement being pumped therethrough without being carried downwardly therewith.